Brown Joseph E, Moreau Jodie E, Berman Alison M, McSherry Heather J, Coburn Jeannine M, Schmidt Daniel F, Kaplan David L
Department of Biomedical Engineering, Tufts University, Medford, MA, 02155, USA.
Department of Plastics Engineering, University of Massachusetts Lowell, Lowell, MA, 01854, USA.
Adv Healthc Mater. 2017 Jan;6(2). doi: 10.1002/adhm.201600762. Epub 2016 Nov 8.
Porous silk protein scaffolds are designed to display shape memory characteristics and volumetric recovery following compression. Two strategies are utilized to realize shape recovery: addition of hygroscopic plasticizers like glycerol, and tyrosine modifications with hydrophilic sulfonic acid chemistries. Silk sponges are evaluated for recovery following 80% compressive strain, total porosity, pore size distribution, secondary structure development, in vivo volume retention, cell infiltration, and inflammatory responses. Glycerol-modified sponges recover up to 98.3% of their original dimensions following compression, while sulfonic acid/glycerol modified sponges swell in water up to 71 times their compressed volume, well in excess of their original size. Longer silk extraction times (lower silk molecular weights) and higher glycerol concentrations yielded greater flexibility and shape fidelity, with no loss in modulus following compression. Sponges are over 95% porous, with secondary structure analysis indicating glycerol-induced β-sheet physical crosslinking. Tyrosine modifications with sulfonic acid interfere with β-sheet formation. Glycerol-modified sponges exhibit improved rates of cellular infiltration at subcutaneous implant sites with minimal immune response in mice. They also degrade more rapidly than unmodified sponges, a result posited to be cell-mediated. Overall, this work suggests that silk sponges may be useful for minimally invasive deployment in soft tissue augmentation procedures.
多孔丝蛋白支架被设计用于展现形状记忆特性以及在压缩后实现体积恢复。采用了两种策略来实现形状恢复：添加诸如甘油之类的吸湿增塑剂，以及用亲水性磺酸化学物质对酪氨酸进行修饰。对丝海绵进行了如下评估：80%压缩应变后的恢复情况、总孔隙率、孔径分布、二级结构发展、体内体积保留、细胞浸润以及炎症反应。甘油改性的海绵在压缩后可恢复至其原始尺寸的98.3%，而磺酸/甘油改性的海绵在水中膨胀至其压缩体积的71倍，远超其原始尺寸。较长的丝提取时间（较低的丝分子量）和较高的甘油浓度产生了更大的柔韧性和形状保真度，压缩后模量无损失。海绵的孔隙率超过95%，二级结构分析表明甘油诱导了β-折叠物理交联。用磺酸对酪氨酸进行修饰会干扰β-折叠的形成。甘油改性的海绵在小鼠皮下植入部位表现出更高的细胞浸润率，且免疫反应最小。它们也比未改性的海绵降解得更快，这一结果被认为是细胞介导的。总体而言，这项工作表明丝海绵可能有助于在软组织增强手术中进行微创部署。
